Process for manufacturing a stacked integrated circuit package

ABSTRACT

In the present invention, memory chips are stuck together in stacked fashion by TAB (tape automated bonding), and a multiple memory chip and lead complex like an SOP (small out-line package) is formed of the chips and leads, whereby a memory module of high packaging density can be realized by a flat packaging technique.

This is a continuation of application Ser. No. 07/890,423, filed May 29, 1992, now abandoned, which is a divisional of application Ser. No. 07/796,873, filed Nov. 25, 1991, issued as U.S. Pat. No. 5,138,438, which is a continuation of application Ser. No. 07/607,411, filed Oct. 3, 1990, now abandoned, which is a continuation of application Ser. No. 07/209,739, filed Jun. 22, 1988, issued at U.S. Pat. No. 4,982,265.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor device. More particularly, it relates to a semiconductor device which is so constructed that a semiconductor chip is put into the form of a module and that a plurality of semiconductor chips are mounted on a module base plate.

A semiconductor device of high packaging density, which is constructed in such a way that a plurality of packages each having a semiconductor chip molded therein are installed on a mounting base plate (a module base plate), is described in "Nikkei Electronics" issued by Nikkei McGraw-Hill Inc., Extra Issue no. 2 "Microdevices," p. 150.

Further, the present invention relates to a technique for installing tape carriers in stacked fashion.

One of techniques for assembling semiconductor elements is the tape carrier system. This system is also termed the "film carrier" or "TAB (Tape Automated Bonding)" system, etc. It is a method wherein semiconductor elements are successively assembled on an elongate resinous tape which is provided with sprocket holes (perforation holes). The tape carrier is such that lead patterns conforming to the electrode arrangements of the semiconductor elements (chips) are formed on a resin film which has the sprocket holes and device holes. By way of exampled the tape carrier is prepared via the steps of slitting a polyimide film coated with a binder, into a proper width; punching the sprocket holes for feed and the device holes for assembling the chips therein, in the slitted film; laminating the punched film with a copper foil; and forming the desired lead patterns by the use of a photoresist technique and an etching technique.

As an example of a literature containing the tape carrier, there is mentioned "VLSI TECHNOLOGY" 1983 Copyright, p. 558, published by McGraw-Hill Book Company Japan.

BRIEF SUMMARY OF THE INVENTION

The inventors studied the semiconductor device referred to before. As a result, the following problem has been found out:

The packages are difficult of reducing their own sizes. It is therefore difficult to heighten the packaging density of the semiconductor chips on the module base plate.

Further, regarding the prior-art tape carrier stated before, the tape carriers of one kind correspond to one predetermined layout and have the same lead patterns. Therefore, the tape carriers of the same kind cannot be installed on a mounting base plate in stacked fashion.

This poses the problem that, when the semiconductor elements are to be installed at a high density, the tape carriers of the same kind need to be juxtaposed on the mounting base plate, so wiring on the surface of the mounting base plate such as a printed-wiring circuit board becomes complicated inevitably. Moreover, the breaking of wire, etc. are prone to occur, and the reliability of the assembled device lowers.

An object of the present invention is to heighten the packaging density of a semiconductor device.

Another object of the present invention is to provide a high-density memory device which is suited to flat packaging.

Another object of the present invention is to provide a memory device which is capable of high-density packaging.

Another object of the present invention is to provide a high-density flat packaging technique which matches well with the TAB (tape automated bonding) technology.

Another object of the present invention is to provide a high-density packaging method which can fully exploit the TAB technology.

Another object of the present invention is to provide a method of assembling memory devices which is capable of simplifying the assemblage and saving labor.

Another object of the present invention is to provide a memory module which can install a large number of memory chips compactly.

Another object of the present invention is to provide a multiple chip and lead complex which exhibits a good solderability at a solder reflow step.

The aforementioned and other objects and novel features of the present invention will become apparent from the description of the specification and the accompanying drawings.

A typical aspect of performance of the present invention will be briefly summarized below:

The bump electrodes of a semiconductor chip are connected to leads, and a plurality of such semiconductor chips having the leads are connected to the wiring of a module base plate, thereby to construct a semiconductor device.

According to the above-stated expedient, the semiconductor chips are not sealed with packages, so that the packaging density of the semiconductor chips on the module base plate can be heightened.

Another typical aspect of performance of the present invention is as follows:

In the present invention, a plurality of tape carriers of an identical kind, the respective lead patterns of which are partly different, are prepared. An alteration for the difference is limited to, for example, only a lead for a chip select signal. Subsequently, the tape carriers thus having the partly different lead patterns are installed on a mounting base plate in stacked fashion.

As described above, the respective lead patterns of the tape carriers to be installed are made partly different so as to permit the stacked installation of these tape carriers, so that semiconductor elements can be installed at a high density, the wiring of the mounting base plate is simplified, and the reliability of the installed device can be enhanced.

In still another typical aspect of performance of the present invention, a semiconductor integrated circuit memory device comprises:

(a) first and second SRAM semiconductor chips each of which is in either of substantially square and rectangular flat shapes and has first and second principal surfaces, said first principal surface being formed with major portions of an SRAM integrated circuit;

(b) a number of electrode pads which are provided near a pair of opposing latera of said first principal surface of said each chip;

(c) a chip select pad which is provided near either of said pair of opposing latera of said first principal surface of said each chip;

(d) a number of leads each of which is made of a metal sheet and an inner end of each of which is connected with a corresponding one of said large number of electrode pads of said each chip;

(e) first and second leads each of which is made of a metal sheet and inner ends of which are connected with the chip select pads of said respective chips;

(f) an insulator member which is interposed between said second principal surface of said first chip and said first principal surface of said second chip extending near the former substantially in parallel therewith; and

(g) superposed connection portions in which parts of and near outer ends of said large number of leads corresponding to said electrode pads having the same functions are respectively superposed and connected so that their extending directions may agree.

In yet another typical aspect of performance of the present invention, a method of assembling a semiconductor integrated circuit wherein memory chips are respectively assembled into a large number of semiconductor chip mounting openings which are provided along a central part of a carrier tape, by connecting them through bump electrodes, comprises:

(a) the step of gang-bonding memory chips having either of the same patterns and substantially the same patterns, to first and second carrier tapes through bump electrodes, respectively,

where each of said first and second carrier tapes has a number of leads made of metal sheets on a first principal surface and in a chip mounting opening, and said first and second carrier tapes have either of substantially the same patterns and the same patterns, except leads which are to be respectively connected with either of chip select terminals and terminals equivalent thereto;

(b) the step of gang-bonding memory chips having either of the same patterns and substantially the same patterns, to corresponding openings of such first and second carrier tapes through bump electrodes, respectively;

(c) the step of superposing said first and second carrier tapes so as to hold the agreeing patterns in correspondence, and pressedly fixing the superposedly extending leads in the respective openings, thereby to form multiple chip and lead complexes each of which includes the plurality of memory chips and the number of leads; and

(d) the step of separating said complexes from each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing the schematic construction of a semiconductor device in Example I of Embodiment 1 of the present invention;

FIG. 2 is a side view showing the schematic construction of the semiconductor device;

FIG. 3 is a front view showing the schematic construction of the semiconductor device;

FIG. 4 is a perspective view of a part of a module base plate (indicated at numeral 1) for explaining a modification to Example I of Embodiment 1;

FIG. 5 is a front view of a semiconductor device in Example II of Embodiment 1 of the present invention;

FIG. 6 is a side view of a semiconductor device in Example III of Embodiment 1 of the present invention;

FIG. 7 is a front view of the semiconductor device in FIG. 6;

FIG. 8 is a plan view of two semiconductor chips in Example IV of Embodiment 1 of the present invention;

FIG. 9 is a side view in which the two semiconductor chips shown in FIG. 8 as confronted to each other and then connected to the same leads are seen in a direction I indicated in FIG. 8;

FIG. 10 is a side view in which the two semiconductor chips connected to the same leads are seen in a direction II indicated in FIG. 8;

FIG. 11 is a plan view of two semiconductor chips (4A and 4B) which are to be stacked over each other; and

FIG. 12 is a side view in which the semiconductor chips (4A, 4B) confronted to each other and then connected to the same leads (5) are seen in the direction I of the semiconductor chip (4A) indicated in FIG. 11.

FIGS. 13(A)-13(C) are principle diagrams showing Embodiment 2 of the present invention, respectively;

FIG. 14 is a plan view of essential portions showing Embodiment 2 of the present invention;

FIG. 15 is a plan view of essential portions showing Embodiment 2 of the present invention;

FIG. 16 is a sectional view showing Embodiment 2 of the present invention; and

Fig. 17 is a sectional view showing Embodiment 2 of the present invention.

FIG. 18 is a circuit block diagram showing the general system of memory modules according to the present invention;

FIG. 19 is a layout plan of circuits and bonding pads on the first principal surface of an SRAM (static random access memory) chip in the multiple chip complex of the present invention;

FIG. 20 is a layout plan of the pins of the memory module of the present invention;

FIGS. 21(a), 21(b) and 21(c) are a top view, a front view and a side view showing the exterior appearance of the memory module of the present invention, respectively;

FIG. 22 is a plan view showing the larger-area property of a tape carrier in the present invention;

FIGS. 23 and 24 are top views of the unit portions of tape carriers (upper stage TAB, lower stage TAB) in the present invention, respectively;

FIGS. 25 thru 28 are sectional flow diagrams showing the wafer process of the SRAM chip in the present invention;

FIG. 29 is an enlarged sectional view of essential portions showing the gang-bonded state between the lead of the tape carrier and the bump electrode of the chip;

FIG. 30 is a sectional view showing the joined situation of the carrier tape and the chip and the coating state of a potting resin;

FIG. 31 is a top view showing the upper stage TAB separated into the unit portion;

FIG. 32 is a top view showing the lower stage TAB separated so as to leave essential parts in the unit portion;

FIGS. 33(a) and 33(b) are a bottom view of a multiple memory chip and lead complex and a sectional view taken along A--A in FIG. 33(a), respectively;

FIGS. 34 thru 37 are sectional flow diagrams showing a process for the flat packaging of the multiple chip and lead complexes like SOPs (small out-line packages) and decoder ICs on a laminated ceramic wiring base plate;

FIG. 38 is a sectional view showing the state of the inserted installation of the memory module on a glass-epoxy printed-wiring base plate;

FIG. 39 is a top view showing the upper stage TAB which has been gang-bonded;

FIG. 40 is a top view of the lower stage TAB similarly gang-bonded;

FIG. 41 is a top view showing the state in which the upper stage TAB and the lower stage TAB are stacked; and

FIGS. 42(a) and 42(b) are a bottom view and a sectional view showing a butt lead type complex which is another embodiment of the multiple chip and lead complex in FIGS. 33(a) and 33(b), respectively.

DETAILED DESCRIPTION OF THE INVENTION

(1) Embodiment 1:

In the ensuing description and the accompanying drawings, parts having the same functions will be indicated by numerals the two lower digits of which are identical, unless otherwise specified. The repeated explanation of the parts shall be omitted to the utmost.

EXAMPLE I

Now, Example I of Embodiment 1 of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view showing the schematic construction of a semiconductor device in Example I of Embodiment 1 of the present invention;

FIG. 2 is a side view showing the schematic construction of the semiconductor device; and

FIG. 3 is a front view showing the schematic construction of the semiconductor device.

Referring to FIGS. 1 thru 3, numeral 1 designates a module base plate which is constructed by stacking pluralities of ceramic layers and wiring layers by the use of laminated ceramic. Eight semiconductor chips 4A, 4B, 4C and 4D are installed on each of the front surface and rear surface of the module base plate 1. Each of the semiconductor chips 4A, 4B, 4C and 4D has, for example, a static RAM constructed therein. Structurally, it is not sealed with a package made of ceramic, a resin or the like, but its surface provided with semiconductor elements and wiring is molded with a resin 7.

Each of the semiconductor chips 4A, 4B, 4C and 4D is provided with bump electrodes 6 which are made of a solder, gold or the like, and to which leads 5A, 5B, 5C and 5D are respectively connected by TAB (Tape Automated Bonding). The semiconductor chip 4A is stacked over the semiconductor chip 4B in such a way that the individual leads 5A are connected to the leads 5B of the semiconductor chip 4B with, for example, a solder. That is, by way of example, the lead 5A for inputting an address signal to the semiconductor chip 4A is connected to the lead 5B for inputting an address signal to the semiconductor chip 4B. Likewise, the lead 5A for inputting/outputting the data of the semiconductor chip 4A is connected to the lead 5B for inputting/outputting the data of the semiconductor chip 4B. In other words, the respective leads 5A and 5B having the same functions are connected by the use of, for example, the solder. The individual leads 5B are connected to a decoder 3 and leads 2 through wiring (not shown) laid within the module base plate 1. In this regard, the lead 5A₁ for inputting a chip select signal to the semiconductor chip 4A is connected to the lead 3A of the decoder 3 without being connected with the lead 5B₁ for inputting a chip select signal to the semiconductor chip 4B. In addition, the lead 5B₁ is connected the lead 3A different from the aforementioned lead 3A to which the lead 5A₁ is connected. One semiconductor chip 4A or 4B is selected from among the eight semiconductor chips 4A and 4B by the decoder 3.

The semiconductor chip 4C is overlaid with the semiconductor chip 4D in such a way that the individual leads 5D of the semiconductor chip 4D are connected to the leads 5C of the semiconductor chip 4C with, for example, a solder. The individual leads 5C are connected to a decoder 3 or leads 2 through wiring laid within the module base plate 1. In this regard, the lead 5D₁ for inputting the chip select signal of the semiconductor chip 4D is directly connected to the lead 3A of the decoder 3 without being connected with the lead 5C₁ for inputting the chip select signal of the semiconductor chip 4C. In addition, the lead 5C₁ is connected to the lead 3A of the decoder 3 different from the aforementioned lead 3A to which the lead 5D₁ is connected. One semiconductor chip 4C or 4D is selected from among the eight semiconductor chips 4C and 4D by the decoder 3. The principal surface, namely, the surface provided with the semiconductor elements and wiring, of each of the semiconductor chips 4A, 4B, 4C and 4D is molded with the resin 7 or silicone rubber 7.

As described above, the semiconductor device is constructed by installing on the module base plate 1 the respective semiconductor chips 4A, 4B, 4C and 4D to which the corresponding leads 5A, 5B, 5C and 5D are connected by the TAB without encapsulation in packages, whereby the area which the single semiconductor chip 4A, 4B, 4C or 4D occupies on the module base plate 1 can be reduced, and hence, the larger number of semiconductor chips 4A, 4B, 4C and 4D can be installed on the module base plate 1. That is, the packaging density of the semiconductor device can be heightened.

Moreover, since the semiconductor chip 4B is overlaid with the semiconductor chip 4A and also the semiconductor chip 4C with the semiconductor chip 4D, the larger number of semiconductor chips 4A, 4B, 4C and 4D can be installed without enlarging the module base plate 1.

Next, a modification to Example I of Embodiment 1 will be described.

FIG. 4 is a perspective view of a part of the module base plate 1 for explaining the modification of Example I of Embodiment 1.

As shown in FIG. 4, a further semiconductor chip 4E may well be stacked over the semiconductor chip 4A. Symbol 5E denotes the leads of the semiconductor chip 4E, which are connected to the leads 5A. In this regard, the lead 5E₁ for inputting a chip select signal to the semiconductor chip 4E is not connected with the lead 5A₁ or 5B₁, but it is connected to the lead 3A of the decoder 3 different from the leads 3A to which the leads 5A₁ and 5B₁ are respectively connected. Although the rear surface of the module base plate 1 is not illustrated, the semiconductor chip 4D is similarly overlaid with a further semiconductor chip on the rear surface so as to form the three-layered structure.

EXAMPLE II

FIG. 5 is a front view of a semiconductor device in Example II of Embodiment 1 of the present invention.

Referring to FIG. 5, symbol 1A denotes a connection terminal on the front surface of the module base plate 1, and symbol 1B a connection terminal on the rear surface thereof. In this example, three semiconductor chips 4B, 4A and 4E constitute one set, and four such sets are arranged on the front surface of the module base plate 1. Likewise, four sets each consisting of three semiconductor chips 4C, 4D and 4F are arranged on the rear surface of the module base plate 1.

In Example II, the principal surface of each of the semiconductor chips 4B, 4A, 4E, 4C, 4D and 4F, namely, the surface thereof which is provided with semiconductor elements and wiring and which is covered with a resin 7, is confronted to the module base plate 1, thereby to shorten leads 5A, 5B, 5E, 5C, 5D and 5F.

EXAMPLE III

FIG. 6 is a side view of a semiconductor device in Example III of Embodiment 1 of the present invention, and

FIG. 7 is a front view of the semiconductor device.

Example III of Embodiment 1 of the present invention is such that a semiconductor chip 4B installed on the front surface of a module base plate 1 has its rear surface confronted to the module base plate 1, while a semiconductor chip 4C installed on the rear surface of the module base plate 1 has its principal surface confronted to the module base plate 1. In this way, when the semiconductor device is viewed from the side of the semiconductor chip 4B, the leads 5B of the semiconductor chip 4B and those 5C of the semiconductor chip 4C having the same functions coincide in projection. The respectively coincident leads 5B and 5C of the same functions are connected by the penetrating wiring (through-hole wiring) 8 of the module base plate 1. That is, each lead 5B is connected to the corresponding lead 5C having the same function as that of this lead 5B by the penetrating wiring 8. Thus, by way of example, the lead 5B for inputting an address signal to the semiconductor chip 4B is connected through the penetrating wiring 8 to the lead 5C for inputting an address signal to the semiconductor chip 4C. Likewise, the lead 5B which serves as an input/output terminal for the data of the semiconductor chip 4B is connected through the penetrating wiring 8 to the lead 5C which serves as an input/output terminal for the data of the semiconductor chip 4C. In this regard, the lead 5B₁ for inputting the chip select signal of the semiconductor chip 4B and the lead 5C₁ for inputting the chip select signal of the semiconductor chip 4C are not connected by the penetrating wiring 8, but the lead 5B₁ is connected to a decoder 3 disposed on the front surface of the module base plate 1, while the lead 5C₁ is connected to a decoder 3 on the rear surface of the module base plate 1. Here, the module base plate 1 in the present example has a single-layer structure which is made of a resin, for example, glass epoxy, and inside which any wiring other than the penetrating wiring 8 is not provided. On the front and rear surfaces of the module base plate 1, however, there are laid wiring for connecting the semiconductor chips 4B, 4C and leads 2, wiring for connecting the decoders 3 (not shown in FIGS. 6 and 7) and the semiconductor chips 4B, 4C, and so forth. The penetrating wiring leads 8 are formed in such a way that through holes are provided in the module base plate 1 by, for example, a drill and are thereafter plated with, for example, copper layers by, for example, evaporation or electroless plating.

As described above, the leads 5B and 5C of the same functions are connected by the penetrating wiring 8, whereby the module base plate 1 is constructed into the single-layer structure inside which no wiring other than the penetrating wiring 8 is provided, so that the reliability of the module base plate 1 can be enhanced.

Moreover, since the leads 5B and 5C of the same functions are connected by the penetrating wiring 8, the number of the wiring leads to be laid on the front and rear surfaces of the module base plate 1 can be decreased.

Incidentally, the module base plate 1 with the penetrating wiring 8 may well be formed of laminated ceramic. In this case, the wiring for connecting the semiconductor chips 4B, 4C and the leads 2, the wiring for connecting the semiconductor chips 4B, 4C and the decoders 3, etc. are buried in the module base plate 1. Owing to the provision of the penetrating wiring 8, however, it suffices to lay for example, only the wiring for connecting the semiconductor chip 4B on the front surface of the module base plate 1 to the leads 2 and the decoder 3, so that the number of the wiring leads to be buried can be sharply decreased. Accordingly, the reliability of the module base plate 1 can be heightened.

EXAMPLE IV

FIG. 8 is a plan view of two semiconductor chips in Example IV of Embodiment 1 of the present invention;

FIG. 9 is a side view in which the two semiconductor chips shown in FIG. 8 are confronted to each other and connected to the same leads, and they are seen in a direction I indicated in FIG. 8; and

FIG. 10 is a side view in which the two semiconductor chips connected to the same leads are seen in a direction II indicated in FIG. 8.

Example IV of Embodiment 1 of the present invention is such that, in a semiconductor chip 4A, bump electrodes 6A are successively arranged from the upper left corner of this chip, while in a semiconductor chip 4B, bump electrodes 6B having the same functions as those of the bump electrodes 6A are arranged from the upper right corner of this chip. More specifically, in the bump electrodes 6A₂, . . ., 6A_(N-1), 6A_(N), 6A_(N+1), . . . and 6A_(N+M) of the semiconductor chip 4A and the bump electrodes 6B₂, . . . , 6B_(N-1), 6B_(N), 6B_(N+1), . . . and 6B_(N+M) of the semiconductor chip 4B, ones having the same suffixes are the bump electrodes of the same functions. The bump electrodes 6A and 6B are symmetrically arranged so that, when the semiconductor chips 4A and 4B are stacked with their principal surfaces confronted to each other, the bump electrodes 6B₂, . . . , 6BN₋₁, 6B_(N), 6B_(N+1), . . . and 6B_(N+M) of the semiconductor chip 4B may overlie those 6A₂, . . . , 6AN_(N-1), 6A_(N), 6A_(N-1) and 6A_(N+M) of the semiconductor chip 4A, respectively. These bump electrodes 6A and 6B symmetrically arranged are connected to the same leads 5. However, the bump electrode 6A₁ for inputting the chip select signal of the semiconductor chip 4A and the bump electrode 6B₁ for inputting the chip select signal of the semiconductor chip 4B are dislocated so as not to coincide, and are connected to the separate leads 5. An insulator member 9 insulates the lead 5 to which the bump electrode 6A₁ is connected, from the semiconductor chip 4B, while another insulator member 9 insulates the lead 5 to which the bump electrode 6B₁ is connected, from the semiconductor chip 4A. By the way, the leads 5 are formed into appropriate shapes after the semiconductor chips 4A and 4B have been confronted to each other and connected to the leads 5. Subsequently, a plurality of sets each consisting of the semiconductor chip 4A and the semiconductor chip 4B are arranged on each of the front and rear surfaces of a module base plate 1.

As described above, the bump electrodes 6A and 6B are arranged symmetrically and are connected to the same leads 5, whereby the density of installation of the semiconductor chips 4A and 4B on the module base plate 1 can be doubled.

As illustrated in FIGS. 11 and 12, it is also allowed to arrange the bump electrode 6A₁ of the semiconductor chip 4A and the bump electrode 6B₁ of the semiconductor chip 4B at symmetric positions, in other words, to arrange the bump electrodes 6A₁ and 6B₁ so that they may coincide in projection when the semiconductor chip 4B is stacked over the semiconductor chip 4A. In this regard, the lead 5 to which the bump electrode 6A₁ is connected and the lead 5 to which the bump electrode 6B₁ is connected are stacked, but they are insulated by the insulator member 9. Incidentally, FIG. 11 is a plan view of the two semiconductor chips 4A and 4B to be stacked, while FIG. 12 is a side view in which the semiconductor chips 4A and 4B are confronted to each other and connected to the same leads 5, and they are seen in the direction I of the semiconductor chip 4A indicated in FIG. 11.

Although, in the above, this embodiment has been concretely described in conjunction with the examples, it is a matter of course that the present invention is not restricted to the foregoing examples, but that it can be variously altered within a scope not departing from the purport thereof.

An effect which is attained by a typical aspect of performance of the present invention will be briefly described below:

A semiconductor device is constructed in such a way that a plurality of semiconductor chips to which leads are connected by the TAB without encapsulation in packages are mounted on a module base plate, whereby the area which the single semiconductor chip occupies on the module base plate can be reduced, and hence, a larger number of semiconductor chips can be mounted on the module base plate. That is, the packaging density of the semiconductor device can be heightened.

(2) Embodiment 2:

Next, Embodiment 2 of the present invention will be described with reference to the drawings.

FIGS. 13(A)-13(C) are principle diagrams showing Embodiment 2 of the present invention. A plastic film tape is provided with device holes 101, and lead patterns 102 formed on the film tape are partly protruded into the device holes 101. In FIG. 13(A), the lead 102a of the lead pattern 102 situated at the upper right end of the figure extends in parallel with the remaining leads 102b, whereas in FIG. 13(B), the lead 102a of the lead pattern 102 situated at the upper right end of the figure is in a shape bent at a right angle. A semiconductor chip, not shown, is assembled in each device hole 101. In FIG. 13(A), the lead 102a at the upper right end of the figure serves as a lead for the chip select signal of the semiconductor chip assembled in the device hole 101, while in FIG. 13(B), the right-angled bent lead 102a at the upper right end serves similarly as a lead for the chip select signal of the corresponding semiconductor chip.

Fig. 13(C) conceptually illustrates the stacked and installed state of tape carriers in which the leads 102a of the respective lead patterns 102 are made different as described above. The lead 102a at the upper right end of this figure governs the input/output of the chip select signal of the upper chip installed stackedly. In addition, the lead 102a adjoining the aforementioned lead 102a governs the input/output of the chip select signal of the lower chip installed stackedly.

The other leads 102b serve as input/output terminals which are common to both the chips. FIG. 14 shows the details of the tape carrier in FIG. 13(A), while FIG. 15 shows the details of the tape carrier in FIG. 13(B).

As shown in these figures, a plurality of sprocket holes 104 for feeding and positioning the plastic film tape 103 are provided at suitable intervals in each of both the side end parts of the tape 103, and the device holes 101 for assembling the semiconductor chips 5 are provided in the central parts of the tape 103. As illustrated in the figures, the chips 105 are joined to the fore end parts of the lead patterns 102 protruded into the device holes 101, by face-down bonding (gang bonding).

The joining operation is carried out by thermocompression by forming bumps 106 at the electrode portions of each chip 105, but it may well be similarly done by forming bumps 106 on the side of the lead pattern 102. After the bonding (inner lead bonding) of the chip 105, a resin mold member 107 is formed by potting with a molding resin as shown in a sectional view of FIG. 16, whereby the chip 105 is sealed.

Tape carrier packages 108 thus molded are stackedly installed on a mounting base plate 109 as shown in a sectional view of FIG. 17.

In FIG. 17, an upper tape carrier package 108a is the tape carrier package having the lead pattern 102 shown in FIG. 13(A), and a lower tape carrier package 108b is the tape carrier package having the lead pattern 102 shown in FIG. 13(B).

The plastic film tape for use in the present invention is constructed of, for example, a polyimide type resin film which has been slitted into a proper width. The lead patterns 102 can be formed by laminating the film tape with, for example, a copper foil and processing the copper foil with a photoresist technique as well as an etching technique. The partial layouts of the lead patterns 102 are made different in accordance with the respective tape carrier packages 108a and 108b.

Each semiconductor chip 105 includes, for example, a silicon single-crystal substrate, and a large number of circuit elements are formed within the chip by well-known techniques so as to be endowed with one circuit function. Concretely, the circuit elements are, for example, MOS transistors, and the circuit function of, for example, a logic circuit or a memory is afforded by these circuit elements.

The bumps 106 are made of, for example, gold (Au).

The potting resin which is used for the molding is, for example, a potting liquid whose principal component is an epoxy resin.

The mounting base plate 109 is, for example, a printed-wiring circuit board.

According to the present invention, as indicated in the embodiment, the leads 102a which are the parts of the respective lead patterns 102 are made different, thereby permitting the two tape carrier packages 108a and 108b to be stackedly installed on the mounting base plate 109. Thus, the density of installation can be made higher than in an assumed case where the tape carrier packages 108a and 108b are juxtaposed on the mounting base plate 109. Besides, in the case of juxtaposing the tape carrier packages 108a and 108b, wiring becomes long and complicated, whereas according to the invention, wiring is short and is simplified, and the rate of the breaking of the wiring lessens, which is greatly contributive to the enhancement of reliability.

Although, in the above, the invention made by the inventors has been concretely described in conjunction with the embodiment, it is a matter of course that the present invention is not restricted to the foregoing embodiment, but that it can be variously altered within a scope not departing from the purport thereof.

By way of example, the embodiment has been exemplified as stacking and installing the two tape carrier packages on the mounting base plate, but three or more tape carrier packages can be stacked. In some cases, tape carrier packages can be stacked and installed on each of both the surfaces of the mounting base plate.

An effect which is attained by a typical aspect of performance of the present invention will be briefly described below:

According to the present invention, high-density packaging is realized with a tape carrier, and a semiconductor device which is advantageous for wiring and which has an enhanced reliability can be provided.

(3) Embodiment 3:

The present embodiment concerns modifications corresponding to Embodiments 1 and 2 described before, and teaches further practicable examples.

FIG. 18 is a circuit diagram of the general system of memory modules in the present embodiment. Referring to the figure, each of RAM1-RAM16 is the MOS type or BIMOS (bipolar-MOS) type integrated circuit chip of a 256-kilobit SRAM (static random access memory), and it has a chip select terminal CS. Each of decoders 1 and 2 is a resin-encapsulated dual in-line type device for a decoder integrated circuit. Symbols I/O1-I/08 denote data input/output pins, and symbols A0-A18 denote address input pins. Shown at WE, OE and DS are a series of control pins. Among them, the pin WE is a write enable pin, and the pin OE is an output enable pin. The pin DS is usually termed the "pin CS," but it differs in function from the CS terminal of the the RAM chip mentioned before. This terminal DS determines either of the upper and lower decoders to be selected, in accordance with an input "0" or "1." Terminals V_(cc) and V_(ss) are power source terminals in a broad sense, and in particular, the terminal V_(cc) is called a "supply voltage terminal," while the terminal V_(ss) is called a "reference voltage terminal." A voltage of 5 [IV] is fed to the terminal V_(cc), and a voltage of 0 [IV] to the terminal V_(ss).

FIG. 19 shows the layout of the first principal surface of each of the memory chips RAM1-RAM16. Referring to the figure, the first principal surface is provided with address input pads A₀ -A₁₄, input/output pads I/O₀ -I/O₇, a write enable pad WE, an output enable pad 0E, a chip select pad CS, a supply voltage pad V_(cc), a reference voltage pad V_(ss), peripheral circuit blocks 211 and 212 such as an address buffer and an I/O buffer, memory mats 213-216 each of which includes 4-transistor MOS-type SRAM cells each having a high-resistance polycrystalline silicon load, X-group circuit blocks 217-218 such as row decoders, and Y-group circuit blocks 219-222 which include column decoders and sense amplifiers and which correspond to the memory mats 213-216 respectively. Numeral 205 indicates an Si single-crystal substrate.

FIG. 20 shows the pin arrangement of the memory modules corresponding to the general layout stated before.

FIGS. 21(a), 21(b) and 21(c) are a top view, a front view and a side view of the memory modules, respectively. Referring to the figures, numeral 209 indicates a laminated ceramic base plate, numeral 231 a chip capacitor which is connected across the terminals V_(cc) and V_(ss) in FIG. 18, and numeral 232 a foot print or soldering pad for the chip capacitor. Sumbols 233a and 233b denote decoder ICs which correspond to decoders 1 and 2 in FIG. 18, respectively. A memory chip complex 234a corresponds to the RAM1 and RAM5 in FIG. 18, and a chip complex 234b similarly corresponds to the RAM2 and RAM6. Complexes 234c and 234d are similar. Further, a chip complex 234e similarly corresponds to the RAM9 and RAM13, and complexes 234f-234 h are similar to the above. Metal leads 235 are brazed to metallized pads on the side surfaces of the ceramic base plate, and they correspond to the respective pins in FIG. 20.

FIG. 22 shows a polyimide tape which is used for the manufacturing method of the present invention. Referring to the figure, numeral 201 designates a device mounting hole (device hole) or perforation, numeral 205 the mounted position of an Si chip (memory chip), numeral 204 a sprocket hole for the automatic feed or positioning of the carrier tape, numeral 241 an isolation hole for isolating common copper wiring on the carrier tape into the wiring of each unit tape portion, and numeral 242 the carrier tape in which a copper sheet having laminated a polyimide sheet is processed into predetermined patterns by photolithography.

FIG. 23 is an enlarged view of the unit portion of an upper tape corresponding to FIG. 22, for mounting the RAM1-RAM4 and RAM9-RAM12 in FIG. 18, in other words, upper chips. Referring to FIG. 23, the upper tape unit is provided with a device hole 201, sprocket holes 204, isolation holes 241, broader copper belts 243, copper leads 244 disposed on the carrier tape 242, outer lead and inner lead regions 245 made of copper sheets, support leads 246 which extend on the tape and into the device hole and which hold the leads at end parts, a copper lead for CS at 247a, a copper plate 248, and copper pads for tests at 249, which are provided in a number of 14 on each of both the sides of the tape. The other straight or bent fine lines indicate copper wiring patterns. Numeral 205 indicates a chip mounting position.

FIG. 24 is an enlarged view of the unit portion of a lower tape corresponding to FIG. 22, for mounting the RAM5-RAM8 and RAM13-RAM16 in FIG. 18, in other words, lower chips. In FIG. 24, symbol 247b denotes a copper lead for CS, and the other patterns are quite the same as in FIG. 23.

FIGS. 25-28 show the flow of a process for forming the bump electrode on the memory chip. Referring to the figures, numeral 205 designates an Si single-crystal substrate, numeral 251 a subbing inorganic insulator film which includes inter-layer insulator films such as a first passivation film of thermal oxidation SiO₂ and a second passivation film of PSG (phosphosilicate glass), numeral 254 an A1 bonding pad which is formed by patterning the same A1 film as an A1 layer for the internal interconnection of the memory chip, numeral 252 a final passivation film made of SiO₂ or Si₃ N₄, and numeral 253 a resin layer made of PIQ (polyimide isoindoloquinazolinedione). Numeral 255 indicates an underlying metal layer which is made of Ti (titanium), and numeral 256 another underlying metal layer which is made of Pd (palladium). Numeral 257 indicates a bump forming photoresist layer, which is used for forming an Au (gold) bump 258.

FIG. 29 is a sectional view showing the state in which the above bump in FIG. 28 and the inner lead in FIG. 23 or FIG. 24 are gang-bonded.

In FIG. 29, numeral 245 indicates the fore end part of the copper inner lead, numeral 259 an Ni (nickel) plating layer, and numeral 260 an Au (gold) plating layer.

FIG. 30 is a sectional view in which the chip in the state of FIG. 29 as potted with a molding resin material over substantially the whole principal surface thereof is shown in relation to the surrounding carrier tape. Referring to FIG. 30, numeral 205 indicates the memory chip, numeral 242 the inner end of the device hole side of the carrier tape, numeral 245 an outer lead portion (Cu film), numeral 258 the Au bump, and numeral 261 a molding resin layer (epoxy type resin).

FIG. 31 is a plan view of the tape carrier (upper side) divided into the individual unit portion at the stage of FIG. 29. In FIG. 31, numerals 281 and 282 indicate Cu test pads which are provided in the number of 14 on the corresponding sides of the carrier tape, symbols 204a and 204b denote sprocket holes, symbol 205a denotes the first principal surface of the upper chip corresponding to the RAM1-RAM4 and RAM9-RAM12 in FIG. 18, and symbols 262a and 262b denote joining regions or pressed connection regions for forming a complex together with a lower carrier tape.

FIG. 32 is a top view showing the state in which the lower carrier tape corresponding to FIG. 31 is separated so as to leave only the necessary parts of the unit portion thereof. In FIG. 32, symbol 205b denotes the upper (first) principal surface of the lower chip corresponding to the RAM5-RAM8 and RAM13-RAM16 in FIG. 18, symbols 262a and 262b denote upper and lower lead joining regions in which the leads of the lower chip and the corresponding leads of the upper chip are pressedly joined so as to be superposed, and symbols 284a and 284b denote sprocket holes.

FIGS. 33(a) and 33(b) are a bottom view and a sectional view (taken along A--A in FIG. 33(a)) of a multiple chip multiplex, respectively. The multiple chip multiplex is prepared in such a way that, after the outer leads of the chip-tape multiplexes in FIGS. 31 and 32 have been joined by thermocompression, the joined outer leads are cut near the edges of the device hole and are finally bent and formed like an SOP (small in-line package). Referring to FIGS. 33(a) and 33(b), symbols 205a and 205b denote the upper and lower chips, respectively (although the upper and lower positions are reversed in the illustration, the upper and lower chips are defined as mentioned above for the sake of the description of an assembling method). Numeral 245 designates the superposed and bent outer leads. Symbols 247a and 247b denote the CS terminal leads of the upper and lower chips, respectively. These CS terminal leads are not superposed and pressedly joined, but they are individually formed into shapes similar to those of the other leads. Numeral 261 and symbols 261a and 261b indicate resin potting layers formed on the first principal surfaces of the respective chips.

FIGS. 34-37 are sectional flow diagrams showing a process in which the multiple chip multiplexes as shown in FIGS. 33(a) and 33(b) are installed by solder reflow on both the surfaces of the laminated ceramic wiring base plate 209 as shown in FIG. 21(a). Referring to FIGS. 34-37, numeral 209 designates the ceramic package base plate, and numeral 263 the outer lead of the module. Symbols 264a-264d denote foot print portions made of metallized layers which serve to solder the multiple chip complexes 234a-234h and decoder ICs 233a and 233b. Solder cream layers 265a-265d are formed on the foot print portions by screen printing. A bonding member 266 serves to hold the multiple chip complex which lies on the lower side during the solder reflow operation. Shown at symbols 267a-267d are solder joint portions which have solidified after the reflow.

FIG. 38 is a sectional installation view showing the state in which the memory modules finished up are soldered and installed on an insertion type printed-wiring base plate by solder waving. Referring to the figure, numeral 271 designates the glass-epoxy wiring base plate, numeral 273 a pin inserting hole, numeral 274 a solder ring pad, numeral 272 a solder resist layer, and numeral 275 a soldering part.

FIGS. 39-41 are plan views of chip-tape multiplexes for explaining the foregoing embodiment and the modifications thereof. Patterns in FIGS. 39 and 40 are quite the same as those of FIGS. 23 and 24, respectively.

FIG. 39 is the top plan of the upper chip lead-tape complex (chip-tape complex). In the figure, symbols 204a14 204h denote sprocket holes, and symbol 205a denotes the upper memory chip which has a CS lead 247a. Numerals 281 and 282 designate Cu test pads which are disposed in every number of 14 on both the sides of the carrier tape. Numeral 293 indicates a part where the corresponding leads of the upper and lower chips brought into pressed contact are cut away from the carrier tape.

FIG. 40 is the top plan of the lower chip-tape complex. In the figure, symbols 284a-284h 7 denote sprocket holes, and symbol 205b denotes the lower memory chip which has a CS terminal lead 247b. Numerals 291 and 292 designate test pads which are arranged in every number of 14 on both the sides of the tape. Shown at numeral 293 is a cutting part for the separation between the tape and the multiple chip complex.

FIG. 41 is the top plan of a stacked state showing an assumed case where the upper tape and lower tape are stacked with the upper and lower patterns thereof held substantially in agreement, in order to explain the embodiment. Regarding the lower tape, only parts different from the upper tape are illustrated. In FIG. 41, symbols 204a-204h denote the sprocket holes, symbol 205a denotes the first principal surface of the upper chip, symbols 247a and 247b denote the upper and lower CS leads, respectively, and numeral 293 indicates the cutting-away part between the multiple chip complexes and the tapes.

Next, the manufacturing process will be described.

First, upper and lower carrier tapes are prepared. Openings shown in FIGS. 23 and 24, except isolation holes, are formed in a polyimide resin film tape 125 μm thick by punching. Subsequently, wiring patterns in FIGS. 23 and 24 are formed by etching a copper foil 35 μm thick. On the whole areas of the wiring patterns, Ni (nickel) barrier layers 259 and Au (gold) layers 260 each having a thickness of 0.5 μm are formed as shown in FIG. 29 by plating.

On the other hand, the steps of memory chips will be described from the viewpoint of a wafer process. As shown in FIG. 25, polycrystalline Si gates and an inter-layer PSG film 251 are formed on an Si substrate (a wafer about 600 μm thick) 205, whereupon A1 bonding pads (each being 100 μm square) 254 are formed simultaneously with A1 wiring for internal interconnections. In forming these A1 portions, an A1 film about 1 μm thick is deposited on the whole area by sputtering and is thereafter patterned by photolithography. Subsequently, a PSG film which is an inorganic final passivation film and which is about 1.4 μm thick is formed by CVD (chemical vapor deposition). Likewise to the above, it is formed with openings by photolithography. Next, a polyimide coating solution of PIQ or the like is applied by spin coating to a thickness of about 2.3 μm. on this occasion, when the surface of the PSG film 252 is subjected to A1 chelation beforehand, the adhesion between the polyimide film 253 and the PSG film 252 becomes favorable. After the polyimide coating operation, the resultant structure is baked for vaporizing a solvent. At the next step, the polyimide film is photolithographically formed with openings which are about 10 μm larger in diameter than the foregoing openings. Thereafter, the polyimide film is baked for hardening.

Further, as shown in FIG. 26, underlying barrier metal films for bump electrodes, namely, a Ti (titanium) film 255 which is 0.18 μm thick and a Pd (palladium) film 256 which is 0.17 μm thick are successively formed by evaporation.

As shown in FIG. 27, a laminated photoresist 257 which is 20 μm thick is stuck on the whole surface, and it is formed with openings by photoetching so as to become about 10 μm larger in diameter than the underlying polyimide openings. Under this state, the Au (gold) bump electrodes 258 are formed in the openings of the openings by the electroplating of Au (gold) at a thickness of about 20 μm.

Next, as shown in FIG. 28, the photoresist film 257 is removed with the Au bumps 258 left behind. Further, using the Au bumps 258 as a mask, the unnecessary parts of the UBMs (underlying barrier metals) are removed by chemical etching or back sputtering. Then, the Au bump electrodes are finished up.

After the electrical tests of the chips in the wafer state, the wafer is divided into the individual chips (4 mm×10 mm×0.25 mm) as shown in FIG. 19 by dicing. Here, before the dicing operation, the wafer is made 250 μm thick by back grinding.

Next, as shown in FIG. 29, the chips are arranged so that their first principal surfaces may assume positions indicated by broken lines 205 in FIGS. 23 and 24, respectively, and a heated tool for TAB bonding is pressed from above, whereby the Au bumps 258 and the Au plating layers 260 of the leads 245 are bonded by thermocompression. This is the so-called gang bonding process.

Subsequently, as shown in FIG. 30, under the state under which a large number of chips are bonded to a long tape 242, a fluid epoxy resin for potting is let fall from above and is cured, thereby to form organic resin molding layers 261 which are about 50 μm thick. Owing to the molding layers, the surfaces of the chips 205 are protected, and the Au bumps 258 and parts of the leads 245 are sealed, while the joining thereof is secured.

Subsequently, in the long tape state and as shown in FIGS. 39 and 40, the upper TAB and lower TAB are subjected to aging and selection tests by utilizing test pads 281, 282, 291 and 292.

At the next step, as shown in FIGS. 31 and 32, the upper and lower TABs are split into units, and the leads are formed like those of SOPs (small out-line packages) so that the portions 262a and 262b of the upper and lower TABs may be stacked. In this case, the upper TAB undergoes little deformation and can therefore have its leads formed in the perfect unit TAB state. Since, however, the lower TAB exhibits a large amount of deformation, the tape is separated near the outermost side of the outer leads.

Next, using the sprocket hole 204a as a positioning hole, the chips are stacked in order to establish the positional relations of the leads as schematically shown in FIG. 41. A bonding tool (tool load: 570-750 gr./lead, tool temperature: 530°-570° C., depressing time: 1-5 seconds) is depressed on the portions 262a and 262b in FIGS. 31 and 32, thereby to bond the corresponding leads by thermocompression.

Next, the carrier tapes and the chip-lead multiplexes are separated by cutting the leads at a cutting part 293 in FIG. 41. In this way, a multiple chip complex whose sectional configuration is as shown in FIG. 33(b) is finished up.

FIGS. 34-37 illustrate the process of installation on a ceramic base plate 209 for memory modules as shown in FIG. 21(a).

First, a ceramic package body as shown in FIG. 34 is prepared. The typical dimensions of a ceramic package are 40 mm in length, 15 mm in width and 2 mm in thickness. Further, the pitch of leads 263 ("42 Alloy" plated with Ni-Si) is 2.54 mm. The ceramic package is made of a multilayer wiring base plate whose material is alumina ceramics.

Subsequently, as shown in FIG. 35, metallized foot print portions 264a-264d on the base plate are overlaid with solder cream layers 265a-265d by screen printing.

Subsequently, as shown in FIG. 36, the multiple chip multiplexes are placed on the upper and lower surfaces of the base plate 209 so that the outer ends of the outer leads and the vicinities thereof may abut on the corresponding solder cream layers. The lower multiplex need to have its rear surface supported by an adhesive or bonding member 266.

Next, the resultant structure is inserted into a reflow furnace at about 220° C. and is thus subjected to reflow soldering as shown in FIG. 37.

Further, as illustrated in FIG. 38, the memory modules are inserted into a printed-wiring base plate 271 made of glass epoxy or the like, and solder waving is applied from below the printed base plate 271 under this state, whereby soldering is completed.

FIGS. 42(a) and 42(b) are a bottom view and a sectional view (taken along B--B in FIG. 42(a)) of a multiple chip-lead multiplex in another embodiment of the present invention, respectively. Referring to the figures, symbols 205a and 205b denote upper and lower memory chips, respectively. Numeral 245 designates leads (outer leads) which are connected to pads having the same function, except pads CS. Symbols 247a and 247b denote outer leads which are connected to the CS pads of the upper and lower chips, respectively. Symbols 261a and 261b denote epoxy resin layers which are formed for potting on the device surfaces of the upper and lower chips, respectively. In case of this example, assembling steps are substantially the same as those of the example in FIGS. 18-41, but only the step of forming the leads needs to be carried out after separating the multiple chip complex from the tape. In this regard, it is also possible that the outer leads of the multiple chip-lead multiplex are bent and formed in the tape state in which the other parts than the support leads 246 in FIG. 23 are separated from the tape. This holds true also of the SOP type stated before.

Although the above description has referred to FIGS. 18-42(b) by taking the concrete TAB systems as examples, the present invention is not restricted thereto.

That is, the examples of FIGS. 18-42(b) are practicable examples for the embodiments in FIGS. 1-17 and are of course applicable to these embodiments.

Further, although only the double chip-lead multiplex has been described in Embodiment 3, triple--quintuple multiplexes and more multiple multiplexes can be performed substantially similarly.

Further, the module wiring base plate is not restricted to the ceramic base plate, but a plastic base plate such as glass epoxy printed-wiring base plate as indicated in a cited reference later can be applied.

Further, the pressed connection of the corresponding outer leads of the upper and lower TABs is possible even in the ong TAB state, and it can be done in the state in which the outer leads are substantially flat.

It is needless to say that, in addition to the above, various technical alterations as indicated in the following cited references are possible.

(4) References for Supplementing the Description of Embodiments:

The details of the wafer processes, device structures, systems etc. of the monolithic chips of SRAMs (static random access memories) are contained in U.S. patent applications Ser. No. 899,404 (filed Aug. 22, 1986), Ser. No. 875,674 (filed Jun. 18, 1986) and Ser. No. 764,208 (Aug. 8, 1985), U.S. Pat. No. 4,554,279 as well as British Patent No. 2,092,826 corresponding thereto, etc. Therefore, these shall form the description of the present invention.

Regarding TAB (tape automated bonding), by way of example, a polyimide tape and copper metallizing thereon, a method of forming bump electrodes for TAB inner lead connection on a semiconductor chip, the gang bonding of TAB inner leads with a chip, and the installing and sealing methods of the TAB inner leads are contained in U.S. patent applications Ser. No. 052,386 (filed May 21, 1987) and No. 946,951 (filed Dec. 29, 1986); "Nikkei Electronics" dated Nov. 27, 1978, pp. 197-211, and the same dated Dec. 19, 1983, pp. 82-85; "Nikkei Microdevices," Oct. 1987, pp. 36-38, and February 1987, pp. 43-44, the same dated Jun. 11, 1984, pp. 148-159, pp. 130-147 and pp. 46-48, and the same, March 1986, pp. 128-135; "Solid State Technology," Mar. 1979, pp. 52-55; "Denshi Zairyo (Electronics Materials), " Sep. 1987, pp. 51-56; "Electronics" dated Aug. 21, 1986, pp. 74-76; "JST News," Vol. 3, No. 2, Apr. 1984, pp. 42-43; "VLSI Technology" by Sze, 1983, pp. 558-570; "IC-ka Jisso Gijutsu (IC-implementation Packaging Technology)" edited by Nippon Microelectronics Kyokai and issued by Kogyo Chosa-kai, pp. 102-175; and "Denshibuhin no Jidokumitate Nyumon (Introduction to Automatic Assemblage of Electronic Components)" issued by Nikkan Kogyo Shinbun-sha on Jul. 30, 1986, pp. 90-100. Therefore, these shall be substituted for the description of the present invention.

Further, a memory module is contained in "Nikkei Electronics" dated Sept. 7, 1987, pp. 99-107, and a method of manufacturing a printed-wiring base plate for the memory module, etc. are contained in "Nikkei Microdevices" dated Jun. 11, 1984, pp. 160-168. Therefore, these shall be substituted for the description of the embodiments of the present invention. 

What is claimed is:
 1. A method of fabricating a semiconductor memory module comprising the steps of:providing first and second semiconductor memory chips having respective first and second sets of terminals, each set of terminals including at least one chip-select terminal and a plurality of non-chip-select terminals; providing first and second plastic film tapes having respective first and second device holes sized to accommodate respective said first and second memory chips; forming a first set of leads on said first film tape, said first set of leads protruding into said first device hole and comprising a first plurality of non-chip-select leads having a first pattern and a first chip-select lead having a first arrangement; forming a second set of leads on said second film tape, said second set of leads protruding into said second device hole and comprising a second plurality of non-chip-select leads having a second pattern substantially identical to said first pattern and a second chip-select lead having a second arrangement different from said first arrangement; bonding said first and second sets of leads to respective said first and second sets of terminals; stacking said first chip bonded to said first set of leads on top of said second chip bonded to said second set of leads with said first pattern superimposed on said second pattern and said first arrangement not superimposed on said second arrangement; bonding each lead in said first plurality of non-chip-select leads to a corresponding lead in said second plurality of leads, said corresponding lead being the lead on which said each lead is superimposed. providing a base plate having a first and a second face; and mounting said stacked first and second chips onto said base plate's first face.
 2. The method of claim 1 wherein said film tape is a polyimide resin film tape.
 3. The method of claim 2 comprising the additional step of forming bump electrodes on said terminals before bonding said leads to said terminals.
 4. The method of claim 2 wherein thermocompression bonding is used to bond said first plurality of non-chip-select leads to said second plurality of non-chip-select leads.
 5. The method of claim 1 comprising the additional step of mounting a stacked third and fourth chip onto said base plate's second face, said stacked third and fourth chips being substantially identical to said stacked first and second chips.
 6. A method of fabricating a semiconductor memory module comprising the steps of:providing a base plate having a first and a second face; providing at least four semiconductor memory chips, each chip having at least one chip-select terminal and a plurality of corresponding non-chip-select terminals; connecting a chip-select lead to said at least one chip-select terminal and corresponding leads to said plurality of corresponding terminals; stacking a first chip on top of a second chip, said first and second chips oriented such that corresponding terminals on said first chips are aligned with corresponding terminals on said second chip; stacking a third chip on top of a fourth chip, said third and fourth chips oriented such that corresponding terminals on said third chips are aligned with corresponding terminals on said fourth chip; superimposing and connecting only said corresponding leads on said first chip with corresponding leads on said second chip; superimposing and connecting only said corresponding leads on said third chip with corresponding leads on said fourth chip; mounting said stacked first and second chips onto the face of said base plate; and mounting said stacked third and fourth chips onto the second face of said base plate.
 7. The method of claim 6 wherein a tape automated bonding process is used to connect the leads to the chip terminals on each chip, said tape automated bonding process including the step of forming said leads on a plastic film tape.
 8. The method of claim 7 comprising the additional step of forming bump electrodes on the terminals of each chip prior to tape automated bonding said leads to said chip terminals.
 9. The method of claim 8 wherein thermocompression bonding is used to connect said first chip's corresponding leads to said second chip's corresponding leads and to connect said third chip's corresponding leads to said fourth chip's corresponding leads.
 10. The method of claim 6 wherein the first chip's chip-select terminal is not aligned with the second chip's chip-select terminal when said first and second chips are stacked and the third chip's chip-select terminal is not aligned with the fourth chip's chip-select terminal when said third and fourth chips are stacked.
 11. A method of fabricating a semiconductor memory module comprising the steps of:preparing a first semiconductor device and a second semiconductor device, said first device having a first rectangular shaped semiconductor chip, first leads and a second lead, said first chip including first external terminals and a second external terminal formed on a main surface thereof, one end of said first leads and said second lead being electrically connected with said first external terminals and said second external terminals respectively, said second device having a second rectangular shaped semiconductor chip, third leads and a fourth lead, said second rectangular shaped semiconductor chip including third external terminals and a fourth external terminal formed on a main surface thereof, one ends of said third leads and said fourth lead being electrically connected with said third external terminals and said fourth external terminal respectively, said first and second chips being substantially identical, said first and third external terminals being arranged at the same positions on said main surface, said second and fourth external terminals being arranged at the same positions on said main surface, said first and second leads extending in a downward direction in a substantially straight line from said first chip and said third and fourth leads extending in a downward direction in a substantially straight line from said second chip; stacking said second device over said first device such that the other ends of said third leads of said second device are directly connected with said first leads, and said second lead of said first device and said fourth lead of said second device are electrically independent from each other; preparing a printed circuit board having a main surface and a rear surface with first electrodes, a second electrode and a third electrode formed on said main surface, said second and third electrodes being electrically independent from each other; and mounting said first and second devices on said primed circuit board such that the other ends of said first leads of said first device are electrically connected with said first electrodes of said printed circuit board, and the other end of said second lead of said first device and the other end of said fourth lead of said second device are directly connected with respective said second and third electrodes of said printed circuit board.
 12. A method of fabricating a semiconductor memory module according to claim 11, wherein each of said second lead and said fourth lead is a chip-selecting signal lead, and wherein said second lead and said fourth lead are arranged in different positions in the plane view.
 13. A method of fabricating a semiconductor memory module according to claim 12, wherein said first and third leads are common signal leads.
 14. A method of fabricating a semiconductor memory module according to claim 11, wherein said first to fourth leads are electrically connected with said first to fourth external terminals by bump electrodes formed on said first to fourth external terminals.
 15. A method of fabricating a semiconductor memory module according to claim 11, wherein said first and second external terminals are arranged along facing sides of said first chip, and wherein said third and fourth external terminals are arranged along facing sides of said chip.
 16. A method of fabricating a semiconductor memory module according to claim 11, wherein said leads are connected to said terminals by a tape automated bonding process.
 17. A method of fabricating a semiconductor memory module according to claim 11, further comprising the steps of:preparing a third semiconductor device and a fourth semiconductor device, said third semiconductor device having a third rectangular shaped semiconductor chip, fifth leads and a sixth lead, said third chip including fifth external terminals and a sixth external terminal formed on a main surface thereof, one ends of said fifth leads and said sixth lead being electrically connected with said fifth external terminals and said sixth external terminals respectively, said fourth semiconductor device having a fourth rectangular shaped semiconductor chip, seventh leads and an eighth lead, said fourth chip including seventh external terminals and an eighth external terminal formed on a main surface thereof, one end of said seventh leads and said eighth lead being electrically connected with said seventh external terminals and said eight external terminals respectively, said third and fourth chips being substantially identical, said fifth and seventh external terminals being arranged at the same positions on said main surface, said sixth and eighth external terminals being arranged at the same positions on said main surface, said fifth and sixth leads extending in a downward direction in a substantially straight line from said third chip and said seventh and eighth leads extending in a downward direction in a substantially straight line from said fourth chip; stacking said fourth device over said third device such that the other ends of said seventh leads of said fourth device are directly connected with said fifth leads, and said sixth lead of said third device and said eighth lead of said fourth device are electrically independent from each other; and mounting said third and fourth devices on said printed circuit board such that the other ends of said fifth leads of said third device are electrically connected with fourth electrodes formed on the rear surface of said printed circuit board, and the other end of said sixth lead of said third device and the other end of said eighth lead of said fourth device are directly connected with respective fifth and sixth electrodes also formed on the rear surface of said printed circuit board. 